1. Field
This invention relates generally to filters. It is particularly directed to a filter device useful for sampling the blood plasma of a dialysis patient.
2. State of the Art
A heterogeneous fluid is a fluid consisting of dissimilar ingredients or constituents. Whole blood, an example of a heterogeneous fluid, consists of specialized cellular elements and a liquid, plasma, in which they are suspended.
Oftentimes, a need exists to sample and analyze the plasma constituent of blood without affecting the other constituents. For example, end stage renal disease ("ESRD") patients undergoing maintenance hemodialysis treatments at home presently send blood samples to laboratories for analysis. The blood sample is analyzed for general chemistry profiles (e.g. electrolyte, plasma hemoglobin, total protein, albumin, and immunoglobin concentrations). Sending out blood samples is tedious and involves a significant loss of the ESRD patient's blood cells. Since ESRD patients are typically anemic, a further loss of red blood cells compounds their anemic condition.
Presently, ESRD patients either ignore the problem of further blood cell loss altogether, or endure a complicated procedure whereby the blood cells withdrawn with a sample are salvaged. To salvage the blood cells, a blood sample is first taken from the patient using a syringe under sterile conditions. The blood sample is then centrifuged, separating the blood cells from the plasma. The blood cells are reinfused into the patient. The plasma sample may then be analyzed.
Since for a large proportion of diagnostic procedures a plasma sample is all that is necessary, a need exists for an inexpensive means for collecting a plasma sample without contributing to further blood loss of an ESRD patient.
Another instance where it would be desirable to analyze an animal's blood plasma without affecting the remaining constituents of the blood is during open heart surgery. During such surgery, it is often desirable to measure various parameters such as blood gas analysis, electrolyte concentration, or plasma concentration of various therapeutic agents, without contributing to unnecessary blood loss. In instances such as surgery it may be desirable to monitor the patient's plasma chemistry several times or even continuously.